Thought I’d set up a new thread on the Piranha mobile sim, (some previous posts in UK and Canada sub-forums) - I cannot find a general discussion forum on Piranha anywhere, and nothing on their own website!

Just got a Piranha mobile sim, dual US-UK number is free, (not Estonia or Isle of Man, so cheap for people to call you), good rates in most locations, though data rates vary by provider in some countries (I've been assured that the sim will try to register on the "preferred" provider with cheaper data, we'll see..)
outside UK and US, it's a call-back system, have to see how reliable that is.
Piranha have the best offering for Canada that I have seen in a global sim - 22c/min within Canada or back to US, and 48c/MB for data.

I’ve been testing the VOIP integration on home wifi in the US: on WIFI people are meant to be able to call you on the same number as the SIM.

So far, the outgoing VOIP integration works well - if on wifi, it uses VOIP (at cheaper-than-skype rates, and decent call quality) and if not, it goes through the mobile network. The same number shows up on caller ID for recipient.
Incoming VOIP is not working, it only routes through the mobile network. Customer service has not been very helpful so far, but only one round.
Not sure if this is an artifact of my Samsung Vibrant.

this is a very good international simcard with really good rates.
a true UK number is attached (not IOM or Jersey), plus US number. local numbers at reasonable prices can also be added for around 70+countries
voip application, with very low rates and free incoming calls everywhere, works fine (both incoming-outgoing) on my samsung y pro duos 2.3.6 android phone.

the only disadvantage discovered is that unaswred calls by the recipient are charged (for a fixed rate) form the time the callback is aswered.
fixed rate for Greece is 0.09gbp per unanswered call.
unaswered calls charge through voip application is not applied, only when the call is placed through the normal gsm way.

Just got this email:
Dear Customer, Piranha Mobile will be reducing Data rates while roaming in the EU, the new price should be around 38p Per Mb a reduction of 12p Per Mb. There will be more reductions throughout the next few months, on roaming Data outside of EU. Please check web site for updates

another update today, makes Piranha very competitive for Canada (where I go a lot, and not many good options)

Dear Customer,
As from today Piranha Mobile will be introducing direct dialling in Canada on the Bell Mobility network and dropping Telus network (for now), we will also be reducing Data rates from £0.29 per Mb to £0.25 per Mb.